Technical Field
Embodiments of the present disclosure relate generally to a power net system for a fuel cell vehicle and methods of controlling the same and, more particularly, to a power net system for a fuel cell vehicle, which is capable of removing voltage at a fuel cell stack and consuming regeneration braking energy, and methods of controlling the same.
Description of Related Art
Fuel cell systems can be applied to eco-friendly-type vehicles, such as a hydrogen fuel cell vehicle. Fuel cell systems typically include, for example, a fuel cell stack for generating electric energy from an electrochemical reaction, a fuel supply device for supplying fuel (e.g., hydrogen) to the fuel cell stack, an air supply device (e.g., oxidizer) for supplying air (e.g., oxygen) for the electrochemical reaction, and a heat and water management system for controlling the operating temperature of the fuel cell stack by externally discharging an electrochemical reaction product of the fuel cell stack (e.g., heat) and performing water management.
A fuel cell load device for lowering voltage at the fuel cell stack is typically connected to the fuel cell stack in order to remove oxygen within the fuel cell stack during or after operation of the fuel cell vehicle. Oxygen introduced into the fuel cell stack is removed along with hydrogen that remains in the anode, as current is consumed through the fuel cell load device. If hydrogen remaining in the anode is not sufficient, the consumption of oxygen is impossible. In order to prevent this problem, a wakeup technology for periodically supplying hydrogen to the anode can be used.
Unlike in an internal combustion vehicle, the fuel cell system requires a separate post-processing process for lowering voltage at the fuel cell stack by removing air that remains in the fuel cell stack after the start-up is off in order to prevent the fuel cell stack from deteriorating and prevent the fuel cell stack from exposure to high voltage. If voltage is formed while oxygen remains in the anode, carbon on the cathode side is corroded and deteriorated. In order to solve this problem, there is a need for a process of removing oxygen within the fuel cell stack, preventing the introduction of additional oxygen, and removing introduced oxygen when the oxygen is introduced. It is also necessary to lower voltage at the fuel cell stack using the fuel cell load device when the fuel cell vehicle collides with another object or when the fuel cell system fails in order to prevent the fuel cell stack from being exposed to high voltage.